The long range goal of this proposal is to develop better ways to prevent and treat osteoporosis. Twenty-six University of California investigators representing nine disciplines have developed six Scientific Projects (SP) and three Feasibility Studies (FS) to accomplish this. Small laboratory, clinical, statistical and administrative cores have been formed to support these Scientific Projects and Feasibility Studies at a considerable dollar savings. Our central theme is osteoporosis and fracture prevention. SP #1 investigates the effect of estrogen administration to postmenopausal women on vitamin D metabolism and intestinal calcium absorption. It should answer the important question, does estrogen increase 1,25-dihydroxyvitamin D production and its free concentration in serum? SP #2 assesses whether endogenous acid production in postmenopausal women contributes to negative calcium balance and will determine if HCO3 administration will correct this abnormality. SP #3 evaluates a new approach to analyzing QCT data of vertebra which could provide key structural information that would permit accurate prediction of fracture. SP #4 tests the accuracy, precision and the applicability of a newly developed high speed (1-2 min) dual photon absorption scanner of revolutionary design to assess bone mineral content at multiple sites. Such an instrument has the potential of solving the major current problem in screening, that of the time required for scanning. SP #6 tests the ability of a coherence treatment program, using synthetic parathyroid hormone and calcitonin, to increase bone mineral content in women patients with established spinal osteoporosis. Two FS' investigate basic bone cell biology and one will evaluate whether a human drug induced model of estrogen deficiency bone loss is suitable for testing new drugs with prophylactic potential.